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Twin Chargers: Why?

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Most of the battery degradation due to fast charging is related to localized heat buildup. At 70A - you will only be charging for about 30 minutes - so not too much heat buildup, but probably enough to make a measurable difference. At 40A you will still be charged in under an hour.
Can this heat buildup be detected and accounted for in the charging process? For example, defaulting to 70A charging and automatically dropping to 40A (and then maybe down to 20A) as necessary to minimize degradation. This would allow the fastest, min-degradation charging sweet spot wouldn't it? With no human hassle/fiddling after initial configuring.
 
Can this heat buildup be detected and accounted for in the charging process? For example, defaulting to 70A charging and automatically dropping to 40A (and then maybe down to 20A) as necessary to minimize degradation. This would allow the fastest, min-degradation charging sweet spot wouldn't it? With no human hassle/fiddling after initial configuring.

The Roadster runs the cooling system to cool the batteries during charging. Their software already tries to find the sweet spot.
 
Most of the battery degradation due to fast charging is related to localized heat buildup. At 70A - you will only be charging for about 30 minutes - so not too much heat buildup, but probably enough to make a measurable difference. At 40A you will still be charged in under an hour.

I think there's a little confusion here. Fast charging is 90 kW, that's 480V / 200A. That will 80% charge an 85 kWh pack in 45 minutes.

40A and 70A charging is at 240V, and is 16.8 kW and 9.6 kW, respectively. At 40A you're talking 6 hours for a full charge, or 10 hours at 70A. These rates will not degrade the pack. Also the pack is actively cooled during charging.
 
I think there's a little confusion here. Fast charging is 90 kW, that's 480V / 200A. That will 80% charge an 85 kWh pack in 45 minutes.

40A and 70A charging is at 240V, and is 16.8 kW and 9.6 kW, respectively. At 40A you're talking 6 hours for a full charge, or 10 hours at 70A. These rates will not degrade the pack. Also the pack is actively cooled during charging.

I'm going to split hairs and point out that all charging "degrades" the pack. Every time you charge or discharge it you make a tiny impact on its useful life. There may be a difference in life after charging at 16.8 kW vs 9.6 kW, but it may be so small it is difficult to measure. We simply don't have the data to be able to say for sure.
Likewise we don't have any data on how much 90kW charging "degrades" the pack. The accepted wisdom is that using a lot of fast charging it gives you less useful life than 16.8 or 9.6kW charging, but nobody knows how much.
Suppose charging at 90kW every time you charged produced a useful life of 2% less than 16.8kW. Is that worth the word "degraded"? I don't think so.
10% less? 20% less? 50% less?
I'd love to have actual data.
 
Can this heat buildup be detected and accounted for in the charging process? For example, defaulting to 70A charging and automatically dropping to 40A (and then maybe down to 20A) as necessary to minimize degradation. This would allow the fastest, min-degradation charging sweet spot wouldn't it? With no human hassle/fiddling after initial configuring.

Sure it could. Generally charger's are set to drop current when hear could cause "substantial" damage to the cells - not just "detectable" or "measurable" wear. No reason it couldn't be done - but also not often a big priority. In the example you gave, a hybrid-rate charging plan might only save a few minutes.

All the chargers drop back when they near full to avoid overcharging.
 
I think there's a little confusion here. Fast charging is 90 kW, that's 480V / 200A. That will 80% charge an 85 kWh pack in 45 minutes.

40A and 70A charging is at 240V, and is 16.8 kW and 9.6 kW, respectively. At 40A you're talking 6 hours for a full charge, or 10 hours at 70A. These rates will not degrade the pack. Also the pack is actively cooled during charging.

All charging degrades the pack. A 70A full charge will not damage the pack. The amount of degradation is generally more when more heat is generated.

Also - I think your numbers are backwards.
 
It might seem like I am arguing about an insignificant point, but I don't think it is insignificant...

The battery degradation from normal use is unknown. The battery degradation from quick charging is unknown.
It is possible that the range of degradation from different normal use cases is wider than the effect of quick charging.
 
can someone explain to me what the High Power Wall Connector and the Twin Chargers are and their significnce? in laymen terms please. I am pretty uneducated about this charging stuff. :tongue::smile:
 
A single charger can handle a normal 50A receptacle. To take full advantage of the 100A HPC requires two chargers.

- You can still use the HPC with a single charger, but it would be dialed down to half the amps.

- You can still use two chargers with a single 50A receptacle, but you wouldn't charge any faster than with a single charger.
 
A single charger can handle a normal 50A receptacle. To take full advantage of the 100A HPC requires two chargers.

- You can still use the HPC with a single charger, but it would be dialed down to half the amps.

- You can still use two chargers with a single 50A receptacle, but you wouldn't charge any faster than with a single charger.

Not layman terms in my opinion, Mycroft :smile:

My shot at it:

- With the High Power Wall Connector and the Twin Chargers, you can juice up at upto 62 miles of range per hour of charging time. Really only needed if your battery is drained and you need to 'fill up' really quickly; very unlikely if your commute is not too much and probably not at all if you plugin religiously to 'top up' every night (as Tesla recommends).

- Without the Twin Chargers, the HPC can only give you upto 31 miles of range per hour of charging time. No different than plugging the (standard, included) Universal Mobile Connector cable into a 240V, 50 A wall outlet (like that for an electric clothes dryer).

- The UMC and the Single Charger (coupled with a 240 V, 50 A outlet) are good enough for daily top ups; can definitely get a drained pack (even the largest, 85 kWh one) juiced up to the recommended 80% within a few hours overnight.

- Getting a 240 V, 50 A outlet (NEMA 14-50 to get technical) installed is a lot cheaper (a couple of hundred $ utilizing a good electrician?!) than buying the HPC and then getting the house ready for 100 A supply (put together, will cost well in excess of $2K?!).

- If your commute is just a handful of miles every day, then, you can conceivably top up from a regular 110V outlet using the UMC and the Single Charger onboard and wait to see if you even need the 240V/50A installation.

- Although Tesla recommends getting the Twin Chargers upfront for those who are paranoid, they didn't rule out making the installation of the second charger in the car possible after the fact.

- The Single/Twin Charger aspect is not relevant if utilizing the proposed Tesla Supercharger network while on the road - those superchargers 'pump' DC directly into the battery pack and bypass the onboard charger(s).

Folks, please correct me if I'm off-base anywhere...
 
I am about the farthest thing from an electrical engineer or electrician or anyone else who knows about this stuff. That said, isn't the power in Kw of an outlet just volts*amps? And, if that's right, wouldn't a 240v*50A=12000w or 12Kw?

If I'm correct then twin chargers would give a slightly higher charge from a 240v, 50A than would single chargers?

Please, someone correct me here. Also, I apologize profusely, and prostrate myself before the Internet Gods, if this same exact question has been asked and answered here.
 
I am about the farthest thing from an electrical engineer or electrician or anyone else who knows about this stuff. That said, isn't the power in Kw of an outlet just volts*amps? And, if that's right, wouldn't a 240v*50A=12000w or 12Kw?

If I'm correct then twin chargers would give a slightly higher charge from a 240v, 50A than would single chargers?

Please, someone correct me here. Also, I apologize profusely, and prostrate myself before the Internet Gods, if this same exact question has been asked and answered here.

The confusion is because the electrical code requires a circuit to be rated at 80% for this type of application. In other words, a 50A circuit protected by a 50A circuit breaker can only draw 80% or 40A. In practice that means the NEMA 14-50 outlet although rated at 50A is only permitted to draw 40A. Hope this clarifies.
 
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To add a little more info; from what I remember of the electrical code, the wiring, circuit breaker and outlet must be rated 125% of the maximum ampere draw. So if a charger is drawing 40A than 40A x 125% = 50A rated wiring, circuit breaker and outlet is needed. We tend to use the 80% method because the math is easier to do in the head.
 
My understanding is that a twin charger could also be beneficial if using a non-Tesla charging station in the wild for a slightly faster charge, correct?

If so, I would lean towards a twin charger in the car rather than a HPC at home.